Data on trends in humans are limited. A landmark study by Herman-Giddens
et al. suggests the age of puberty in girls has decreased
in the US. Other studies of specific populations reveal associations
between early sexual development and exposure to contaminations.
Some case histories in medicine document the ability of estrogen
containing compounds to alter the pace and pattern of sexual development
in boys and girls.

In a study of girls exposed in the womb and through breastfeeding
to PBBs because of a food contamination incident in Michigan in
1973, Blanck et al. report that elevated PBB levels are associated
with earlier menstruation and early pubic hair appearance, but not
early breast development. More...

Colón
et al. show that young girls in Puerto Rico suffering from premature
thelarche
carry blood levels of the phthalate DEHP almost 7-fold higher than
controls from the same area. The authors suggest that this anti-androgen
may be intefering with sexual development in young girls. More...

Herman-Giddens
et al. report that girls in the United States are developing
pubertal characteristics earlier than currently-used norms. Inadequacies
of earlier studies make it impossible to reach certain conclusions,
but based on these data, it would appear that white girls in the
current study appear "to be developing 6 months to 1 year sooner
than girls in these earlier studies." More...

Halperin
and Sizonenko describe the case of a boy and his sister, both of
whom displayed signs of breast development, the boy at age 6, the
girl at age 10. It was discovered that they had been imitating their
mother by applying an ointment, Percutatrine, which contained estrone,
DES and extracts of ovaries. The mother had been applying the ointment
to develop her own breast. As soon as this exposure was discovered
it was terminated. The girl's sexual development then returned to
normal.The boy's breast development persisted for about 3 years
after his examination but thereafter was normal, except that his
nipples remained hyperpigmented.

Beas
et al. describe infants showing manifestations of early puberty
that were caused by application of an ointment, Vas-Vit, to the
skin. Tests of the estrogenicity of the ointment confirmed its biological
activity. Once application of the ointment stopped, symptoms of
early puberty regressed.